Double base propellant powder and process of making the same



Patented I mt. mm QFF WILLI AM n. "WAGNER, or AL'rom'ILLmors, ASSIGNOR TQ wnsrnmv can-Tainan oomranger ALTON,' ILLIN OIS, A conrona'rr'on or DELAWARE no Drawing. Application m a rii 7,

1 11 burning, in order to start the projectile charge int-o motion gradually; for a fast generation of gas before the 'pro]ect1le charge has moved any appreciable distance i I will result in high pressures due-to the con- 515 lined space in which the gas must be accommodated. As the projectile charge moves along the barrel and increases in velocity, the efiective volume in the powder chamber is increased so rapidly that gas is not evolved at a rate suiiiciently hi h to maintain a uniform pressure beyond the point at which the maximum pressure occurs. It is desirable that the initial pressure be limited, while the pressure along the barrel should be maintained. In order to maintain the pressure along the barrel, the core of the grain should be as fast burning as possible, while the outside surface of the grainshould have its burning rate reduced. While the rate of ignition and, therefore, the initial rate of evolution of the gas can be controlled to a certain extent by coatin or im re natin the powder grains,'sucli as nitro-cellu- ,QSL pOW(l8I as dinitro-toluene, the bulk of the grain is of a unirorm burning rate, so that the rate of the evolution of the gas does not increase sufiiciently; accordingly, there is a too rapid fall of the pressure as the projectile charge moves along the barrel. a a

One of the objects of this invention, therefore, is to provide a double base powder grain which will meet the requirements noted above and overcome the limiting features of powder grains as heretofore produced.

Another object of this invention is to pro vide a double base powder grain, in which the rate at which the gas is evolved will progressively increase as the grain is consumed. Further objects will appear from the de This invention relates to propellant-'pow-;

ders of the double base type, such as nitro cellulose-nitroglycerin powders. The'illus-" grains, with a deterrent such nounmi BASE rnornntanr row/nun AND rnoonss vor Maxine TEE'SAIIIE 1330. Serial No. 442,4.52.

(-LU n an description, in which there will be specifically described an illustrative embodiment of this invention. It is to be understood, however, that this invention is suscep-' tible of various embodiments within the pur-. view of those skilled-in the art. 7

' Generally stated, in accordance with this invention, a double base powder, such as nitro cellulose W, 15 treated to partially extract one of t 1e. ases, such as nit-ro-glycerin, from the grain so thatthe percentage. content of the partially extracted base and therefore the potential energy per unit weight of the powder will increase as the powder grains burn from the outside towards the center. This is accomplished in accordance with one embodiment of this invention, by treating the grain with an agent or solution which 18 a solvent for; say, the nitro-glyeerin but which is a nonsolvent'f6r HE larger part of the mtro-cdlliilbse. While this results in a grain having generally the characteristic described, there ment of this invention the rain is treated with a deterrent or lasticizer. In ord'e'r"to a p 151 stillfurther the partial ext-ra tion of the nitro-glycerin from the surface of the grain and in order to secure the desired increase or taper effect from the surface to the interior of the grain, the double base grain is, after an initial treatment with a solvent for Intro-glycerin, which is a,non-, solvent for the bulk of the nitro-cellulose, treated in order "to extract the dissolved nitro-glycerin the solution remaining in and on the grain after the bulk of the solution has been removed. Thus after treatment to extract a portion of the nitroglycerin in accordance with this invention the solution may have a nitro-glycerin content of from 6 to 12% and in the grain itself there will be a much more concentrated solution of nitro-glycerin. In order therefore 3 to prevent this nitro-glycerin from being i redeposit-ed on and near the surface of the 3 grains when the volatile solvent for nitrofglycerin left on the grain is evaporated, the powder is given an additional short wash of a'-"fresh solution of nitro-glycerin solvent.

The grain can then be dried to extract the isolvent therefrom. lVhile this treatment 10 tend to againdistribute it throughout themoved and. which gelatinizeris containing 60 nitro-cell nitro-slvcerin. pro uced 1n any manner well.-

r n diameter.

will result in a grain having the desired tapering effect, after an extended time under storage conditions, there may be a gradual migration-of the nitro-glycerinwhich may grain. In accordance with an embodiment of this invention, therefore, the grain is treated with another gelatinizerto replace part of the nitro-gly'cerin which has been readeterrent'and [or a plasticizer; v

As an illustrative embodiment of this invention, we will take a double base powder 7.

known to those skilled in the art. I In a powder adapted more particularly for use in rifles-of small calibre, thegrains may be flat -discs- .050-.075 mm. thick. an

p" in benzol, which is a solvent for n1tro-glyc-.

erin ut anon-solvent for nitro-cellulose. The soaking period is extended to the desired limit. five (5) hours being found pract-ical. At this point the grain can be treated with a suitable elatinizer which is preferably a deterrent and plasticizer, such as dibutvl 1t ialate in a sulta e solvent such as benzol. 'I he gram can then-be-dried. The

timeot soaking is. dependent on the nature in-order to more com letel Y extract thenitroe glycerin; thisis p1 cc-omphshed before the grains are dried and-immediately 5 after they have received their first treatment;

with benzol. The time of treatment will; at course, varywith the character ofsolvent used; thus in the case of benzol the'treat- 6 ment can be carried out for about five (5) minutes. The grains can then be dried in any suitable manner so as to evaporate the solvent, but preferably in a closed system with a solvent recovery. The grains can then be treated with asuit-able, inifzfeffprefe Q ablv "a deterrent and plasticizer such as glibutyl phthalaje For this purpose to 100 parts by"wei'g'ht of powder treated for the removal of nitro-glycerin are added 70 parts by -weight of a 6.75% solution of diamyl phthalate in benzol preferably ina rotating barrel with solvent recovery system. The benzol is driven ofi leaving the diamyl J phthalate in the grain in combination with the nitrocellulose and the remaining nitropreferably;

glycerin. Afterthe i dfygit ean be graphited in thesnsua manner. 1:

It has been found that a double b powder treated as above described will attain the objects of this invention. The progressive burning quality imparted to the powder allows the powder charge of the cartridges to be increased without increasing Charge Average average Powder (grams) pressure velocity Untreated 13, 704 892 Treated".-. 2. 35 13, 708 1, 231

A furthertest showed that the highvelocity bullet with treated powder penetrated twice as far into wood as the lower velocity bullet fired. with the untreated powder. A microscopic examination of the un treated double base grain reveals the fact that the interior of the grain does not consist. of auniformly gelatinized mixture of Intro-glycerin and nitro-cellulose but suggests that there are. centers scattered throu h the, body of the grain which-are very ighin nitro-glycerin content with inter spaces correspondingly low.

A,microscopioexamination after the initiali treatment-with benzol to remove nitroglycerin: indicates that thebenzol attacks thae high centers with great difiiculty which accounts for. the observed fact; that extended treatment does not have much efiect in removing more thanabout 60% of the original content-bf nitrovglycerin and also explains ai'nsmany: times thicker can be sucy cessi-ifig," treated and enough nitro-glycerin removed, for: the successful application of this invention inlthejsame aeriod of timeas for the thinner grains. he extraction of nitroglycerin decreases with the penetration and is less, adjacent to the centers 01'' high Introlycerin; content, in accordance with the W931 known. scientific fact that the rate of difiusion of'two liquids depends upon the difference of concentration; accordingly the more nitro-glycerin the solvent contains at any point within the grain, the less active it becomes in removing nitroglycerin. Accordingly the undissolved nitro-glycerinleft in the grain will taper from the: outside towards the center with centers of high nitrroeglycerincontent distributed throughout the mass, and separated from each other by nitro-cellulose from which the Intro-glycerinhas been .lar ely removed.

The depth of penetration an the extent to asei:

ch the nitro-glycerin is removed from body of the grain will depend upon the er of the solvent and the period of tment.

A microscopic examination of the grain "ter the final treatment with benzol indihroughout the entire mass of the grain, being more concentrated in the areas of low nitro-glycerin content and less concentrated where more nitro-glycerin has remained in the grain. It is seen, therefore, that the resulting powder grain has an exterior of a slow burning combination of nitro-cellulose with a deterrent which is alsoa gelatinizer and plasticizer, and that from the outside towards the center of the grain and also toward the centers of high nitro-glycerin content there is a gradual decrease of deterrent and increase of nitro-glycerin which results in a progressive burnin powder characterized by the fact that t e rate of gas evolution increases as the grains burn from the outside towards the center.

While this invention is particularly applicable to nitro cellulose nitro glycerin powders, gelatinizers for nitro-cellulose, other than nitroglycerin, may be employed, such as nitrates of lv lvcerin, or any of the glyco s or 330 vglvcols. or nitrates of any 015W or in fact any substance which when mixed with or gelatinizcd with nitro-cellulose increases the rate at which gas is evolved over powder gelatinized by the customary solvents, such as acetone or'ether-alcohol. twill be understood, of course, that the nitro-cellulose may be of varying degrees of nitration best suited for the particular substance with which it is combined and the purpose for which it is employed. The solvent employed may be benzol, ethvl alcohol, mqgzhyLzlmlml, ether or any other suitable so vent or mixture oi solvents adapted for that purpose. The solvent may be one which may slightly dissolve the nitro-c'ellulose but not sufficiently to cause the grains to stick together. The gelatinizer may be l hthalate, dia-myl ,hthalate. t-ricresv' Fiospliate but 1 stearale, H QtI'O-tOIHGDQ d imethvl diphenvlurea or any oTher suitable deterrent or plastlclzer.

The deterrent or plasticizer may be applied with any suitable s'rzlvent which may be a solvent only for the piasticizer without being a solvent for nitro-,glycerin or nitrocellulose such as carbon tetrachloride in the case of diamyl phthalate or it may be a solvent for the plasticizer and the nitro-glycerin as in the case of benzol, or it '2 way be a solvent for the plasticizer, nitro-glycerin and a solvent for lower grades of Intro-cellulose, such as methyl alcohol, or'a mixture of a solvent and non-solvent for nitro-cellulose,

such as ethvl acetate and benzol in such proportions t at it wi not actively attack the tes that the plasticizer distributes itselfnitro-cellulose, causing the powder grains to adhere one to-the-other. I ,Itwill furthermore bis understood that certain features and sub-combinations are of utility and-maybe employed without reference "to other features and sub-combinations; that is contemplated byand is within the scope of the appended claims. It is, furthermore, to be understood that various changes may bemade in details and operations within the scope of the appended claims, without departing from the spirit of this invention. It is, therefore, to be understood-that this invention is not to be limited to the specific details and operations described. Having thus described is'claimed isz' V 1. A process of treating double base pow ders, comprising, partially extracting the more active base from a gelatinized part of a double base grainl f 2. A process oitreatin double base powders, comprising, part-ia y extracting the the invention, what more active base' 'from the exterior of a double base'grain.- 3. The process of controlling the ignition or burning characteristics of a double base powder grain by partial extraction of the more active base from the exterior of the grain. 4. A process of treating double base pow ders, comprising, partially extracting the more active base from the grain and replacing the'extracted base with a gelatinizer for the other base.

5. A process -of treating double base powders, comprising, partially extracting the more active base from the grain and re placing the extracted base by a slower-b ii'ningtomponent' 6. A -process of treating double base powders, comprising, partially extracting the m ore active base from a doublebase grain so that the content of the partially extracted base will decrease from the interior to the surface of the grain.

7. A process of' treating double base powders, comprising, partially extracting the more active base from a double-base grain so that the'content of the partially extra'cted base will decrease'from the interior to the surface of the grain, and treating the grain with a deterrent. 7 a

8. A process t improving the ballistio properties of double base powders, comprising, removing part of the more active base by treating a double base grain with an agent which is a solvent for the more active of the bases but a substantially nonsolvent for the other base.

9. A process of treating nitro-cellulosenitro-glycerin powder grains, comprising, partially extracting the nitro-glycerin from the grain.

,10. A process of treating nitro-cellulosepartially extracting the nitroglycerin from the grain and replacing. the extafactednitgoglycerin with a slower-bnrningcoin ODGQL) IL pr rea ing.- A m- 1 .1 6-

nitro-glycerin powder grains-comprising, partially extracting the nitro-glycerin from the grain so that the Intro-glycerin contentwill decrease from. the. interior to-.t l xe surface 10 of the grain. 5 p

12. A process, of improving the ballistic properties of nitrocellulose-nitroglycerin powder grains comprising, removing part .r oi the nitro-glycerinby treating-thegrain L with arsolvent for nitrolycerin which is substantially non-solvent or nitro cellulose.

13, A process of ti eating nitro-cellnlose- .fnitro-glycerin powder grains, comprising,

remoting part of the nitro-glycerin by treatr ing the grain with a solvent forvni tro-glycerinwhich is substantially non-solvent for; intro-cellulose and treating-the grain to extract the dissolved nitro-glycerin. therefrom. 14.; A process of; treating nitrog-cellulose nitfro glycerin powder grains, comprising,

' treating the grain with a solvent for nitroglycerin substantially non-solvent for nitrocellulose and treating the grain with a deterrent. r

15. A double base propellant powder grain the content of the more active base of which decreases from the interior to thesur: face of the grain.

16. A double base. propellant powder grain the content of the inoreactive base of;

which-decreases from the interior to the surface-oi the grain and which is impregnated or coated with a slower-bur o component.

. Hz;Lnitro-cellulose-nitro-g ycerin powder grain whose nitro-glycerin content is revdffe'd near the surface of the grain.

yc p enigr i i mpr e t 8. A nitro-cellulose-nitroglycerin. power grain whose nitro-glycerin content is.

reduced near the surface of the grain. and

which is impregnated or coated with a deterrent.-

19. A' process of making double base powders, comprising, partially extractinv the more active base. from the. grain and V replacing the extracted portion with an ina ".3?" 1" gradient having a different combustion rate f. than the extracted base. n

In testimony whereof I afiix my signature this 1st day oi -April, 1930. v

WILLIAM E. WA NER."

ERTI FICATE 0F CORRECTION. Patent No. 1,906, 675.

A fay 2, 1933. WILLIAM E. WAGNER. i E

I It is hereby certified that error appears in the printed specification of the above numbered patentrequxrmg correcho'x as follows; Pa 10, for "successively" read ge 2, lines 109 and id Letters Patent ay conform to the successfuHy'E should he read record of the c ase in the Patent Office Signed and sealed this 1st day of A ugust A. D. 1933.

- M. J. Moore. (Seal) Acting Commissioner of Patents. 

